content: package com.introlab.rtabmap;
  
  /*
   * Copyright 2017 Google LLC
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  import android.app.Activity;
  import android.content.Context;
  import android.hardware.camera2.CameraAccessException;
  import android.hardware.camera2.CameraCharacteristics;
  import android.hardware.camera2.CameraManager;
  import android.hardware.display.DisplayManager;
  import android.hardware.display.DisplayManager.DisplayListener;
  import android.view.Display;
  import android.view.Surface;
  import android.view.WindowManager;
  import com.google.ar.core.Session;
  
  /**
   * Helper to track the display rotations. In particular, the 180 degree rotations are not notified
   * by the onSurfaceChanged() callback, and thus they require listening to the android display
   * events.
   */
  public final class DisplayRotationHelper implements DisplayListener {
    private boolean viewportChanged;
    private int viewportWidth;
    private int viewportHeight;
    private final Display display;
    private final DisplayManager displayManager;
    private final CameraManager cameraManager;
  
    /**
     * Constructs the DisplayRotationHelper but does not register the listener yet.
     *
     * @param context the Android {@link Context}.
     */
    public DisplayRotationHelper(Context context) {
      displayManager = (DisplayManager) context.getSystemService(Context.DISPLAY_SERVICE);
      cameraManager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
      WindowManager windowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
      display = windowManager.getDefaultDisplay();
    }
  
    /** Registers the display listener. Should be called from {@link Activity#onResume()}. */
    public void onResume() {
      displayManager.registerDisplayListener(this, null);
    }
  
    /** Unregisters the display listener. Should be called from {@link Activity#onPause()}. */
    public void onPause() {
      displayManager.unregisterDisplayListener(this);
    }
  
    /**
     * Records a change in surface dimensions. This will be later used by {@link
     * #updateSessionIfNeeded(Session)}. Should be called from {@link
     * android.opengl.GLSurfaceView.Renderer
     * #onSurfaceChanged(javax.microedition.khronos.opengles.GL10, int, int)}.
     *
     * @param width the updated width of the surface.
     * @param height the updated height of the surface.
     */
    public void onSurfaceChanged(int width, int height) {
      viewportWidth = width;
      viewportHeight = height;
      viewportChanged = true;
    }
  
    /**
     * Updates the session display geometry if a change was posted either by {@link
     * #onSurfaceChanged(int, int)} call or by {@link #onDisplayChanged(int)} system callback. This
     * function should be called explicitly before each call to {@link Session#update()}. This
     * function will also clear the 'pending update' (viewportChanged) flag.
     *
     * @param session the {@link Session} object to update if display geometry changed.
     */
    public void updateSessionIfNeeded(ARCoreSharedCamera session) {
      if (viewportChanged) {
        int displayRotation = display.getRotation();
        session.setDisplayGeometry(displayRotation, viewportWidth, viewportHeight);
        viewportChanged = false;
      }
    }
  
    /**
     *  Returns the aspect ratio of the GL surface viewport while accounting for the display rotation
     *  relative to the device camera sensor orientation.
     */
    public float getCameraSensorRelativeViewportAspectRatio(String cameraId) {
      float aspectRatio;
      int cameraSensorToDisplayRotation = getCameraSensorToDisplayRotation(cameraId);
      switch (cameraSensorToDisplayRotation) {
        case 90:
        case 270:
          aspectRatio = (float) viewportHeight / (float) viewportWidth;
          break;
        case 0:
        case 180:
          aspectRatio = (float) viewportWidth / (float) viewportHeight;
          break;
        default:
          throw new RuntimeException("Unhandled rotation: " + cameraSensorToDisplayRotation);
      }
      return aspectRatio;
    }
  
    /**
     * Returns the rotation of the back-facing camera with respect to the display. The value is one of
     * 0, 90, 180, 270.
     */
    public int getCameraSensorToDisplayRotation(String cameraId) {
      CameraCharacteristics characteristics;
      try {
        characteristics = cameraManager.getCameraCharacteristics(cameraId);
      } catch (CameraAccessException e) {
        throw new RuntimeException("Unable to determine display orientation", e);
      }
  
      // Camera sensor orientation.
      int sensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
  
      // Current display orientation.
      int displayOrientation = toDegrees(display.getRotation());
  
      // Make sure we return 0, 90, 180, or 270 degrees.
      return (sensorOrientation - displayOrientation + 360) % 360;
    }
  
    private int toDegrees(int rotation) {
      switch (rotation) {
        case Surface.ROTATION_0:
          return 0;
        case Surface.ROTATION_90:
          return 90;
        case Surface.ROTATION_180:
          return 180;
        case Surface.ROTATION_270:
          return 270;
        default:
          throw new RuntimeException("Unknown rotation " + rotation);
      }
    }
  
    @Override
    public void onDisplayAdded(int displayId) {}
  
    @Override
    public void onDisplayRemoved(int displayId) {}
  
    @Override
    public void onDisplayChanged(int displayId) {
      viewportChanged = true;
    }
  }
  